A method for treating stenosis caused by arterial plaque, a thrombus, or the like can include percutaneous transluminal coronary angioplasty (PTCA) for dilating a blood vessel by using a balloon, a method for causing a stent having a mesh shape or a coil shape to indwell into the blood vessel as a support for the blood vessel, and atherectomy for scraping off stenosis substances. Any one of these methods has a possibility that an object (debris) formed by stenosis substances being collapsed during treatment may flow through the blood vessel. If the debris flows to a peripheral blood vessel, there is a possibility that new stenosis may occur in the peripheral blood vessel. A method for preventing this possibility can include a method for collecting the debris by installing a wire-woven filter, which can expand and contract inside the blood vessel during treatment of a stenosed site and by using the filter, for example, refer to JP-A-2002-102231. However, in a case of treatment of the stenosed site in a thick and large blood vessel, a long stenosed site formed in arteries of the neck or lower limbs, the amount of debris can increase, thereby causing a possibility that the filter may eventually become full of debris. In this case, the debris cannot be collected by contracting the filter and pulling the filter into a guiding sheath. Thus, it can become necessary to withdraw the filter together with the guiding sheath from a living body while the filter remains in a state of protruding from the guiding sheath. Consequently, this case can require complicated manipulation skill, and the debris collected by the filter may be scattered to a peripheral portion.
As a countermeasure to be taken when a filter is full of debris, a method may be considered which decreases the amount of debris by causing a catheter to aspirate the debris inside the filter. Incidentally, a filter disclosed in JP-A-2002-102231 can be configured so that an edge portion of an opening for receiving the debris of the filter spreading in a basket shape is fixed to a shaft portion extending extracorporeally. Therefore, if an aspiration catheter is pushed into the filter by the above-described shaft portion serving as a guide, the aspiration catheter can be guided to an edge portion of the filter. However, the aspiration catheter cannot be guided into the filter where the debris is collected. Therefore, the debris collected in the filter cannot be effectively aspirated by using the aspiration catheter.